Martin Luther King, Jr. secured federal copyright protection to his “I Have A Dream” speech.
He understood the value and importance registering the copyright to his work
Because of his registration his estate now controls the use of the work.
http://www.law.cornell.edu/copyright/cases/194_F3d_1211.htm
http://www.archives.gov/northeast/nyc/exhibits/mlk.html
Copyright is important to anyone who creates original works of authorship. That includes you as a photographer.